1. Field of the Invention
The present invention relates to an apparatus for detecting specific information such as a digital watermark in a high-speed data stream including data in which the specific information is embedded.
2. Description of the Related Background Art
It is necessary to prevent illegal copy of recorded information such as image information recorded on an optical recording medium such as a DVD. Recently, much attention has been paid to technology for transmitting image data in which a so-called digital watermark is embedded, or for recording the image data on a recording medium. The digital watermark is an inconspicuous image pattern like a small noise component, which indicates information such as copyright information and copy guard.
Since a high-speed data stream such as an MPEG data stream obtained by reading information recorded on for example, a DVD includes a digital watermark component, all the high-speed data stream is processed in real time by a watermark information detecting apparatus to detect the digital watermark component.
A conventional watermark information detecting apparatus necessarily includes a high-speed parser for analyzing the data configuration of a high-speed data stream at high speed, and a high-speed watermark detector for detecting watermark information from a predetermined part of the data configuration analyzed by the high-speed parser.
Recently, a DVD-ROM drive has been used as an external storage device for personal computers. The DVD-ROM drive can usually read recorded information from a disc at high speed which is for example, eight times as fast as the normal speed. In the high-speed DVD-ROM drive, the output speed of a data stream which is read becomes much faster, so that it becomes more difficult to process watermark information by a watermark information detecting apparatus in real time. In addition, if a high-speed watermark decoder for the faster data stream is disposed in the watermark information detecting apparatus, the apparatus will become more expensive.